1. Field of the Invention
This invention relates to a method of producing a granular product from an admixture of a powdery material and a binder and an apparatus for carrying this method into practice.
2. Prior Art
There are known a variety of granulating machines for processing particulate or powdery materials into granules of a predetermined size. A typical conventional high-speed granulator is shown in FIGS. 10a and 10b which is designed to produce a granular article by mixing a starting fine particulate material with stirring. This granulator comprises a disc-like rotor 100 rotatably mounted in a casing 101 and adapted to admix a particulate feedstock F with a liquid binder B fed from above. This admixture is centrifugally forced against the peripheral wall 102 of the casing 101 and vigorously stirred by the action of blades 103 secured peripherally to the rotor 100 until there is produced a continuous flow of product granules of a size determined by a given spacing or clearance between the blade 103 and the casing wall 102. The particulate material F when mixed with the binder B assumes the form of a viscous paste and tends to deposit on the casing wall 102 where indicated at D in FIG. 10b over an extended period of operation. This would result in reduced or varied spacing between the blade 103 and the casing wall 102 and hence irregular or otherwise defective granular product. In a worst instance, the deposit D would grow so large as to reach and interfere the normal rotation of the blades 103, leading to ultimate shut-down of the machine.
It has been proposed to use a resilient material such as synthetic rubber, rubber/cloth composite and the like for a tubular wall member corresponding to the casing wall 102 such that deposit D accumulated thereon can be scraped off by knocking the tubular member from outside at certain time intervals during operation of the machine. However, the use of such resilient tubular wall entailed a difficulty in maintaining a proper wall to blade spacing so that the resulting granular product would become irregular in its size or diameter, not to speak of the resilient wall being susceptible to physical deformation or damage due to repeated knocking.